Sunday, June 25, 2006

Ice caps

Climate experts have started to worry that the ice cap is disappearing in ways that computer models had not predicted.

By all accounts, the glaciers of Greenland are melting twice as fast as they were five years ago, even as the ice sheets of Antarctica — the world's largest reservoir of fresh water — also are shrinking, researchers at NASA's Jet Propulsion Laboratory and the University of Kansas reported in February.

Zwally and other researchers have focused their attention on a delicate ribbon — the equilibrium line, which marks the fulcrum of frost and thaw in Greenland's seasonal balance.

The zone runs around the rim of the ice cap like a drawstring. Summer melting, on average, offsets the annual accumulation of snow.

Across the ice cap, however, the area of seasonal melting was broader last year than in 27 years of record-keeping, University of Colorado climate scientists reported. In early May, temperatures on the ice cap some days were almost 20 degrees above normal, hovering just below freezing.…

Indeed, Zwally and his colleagues in March released an analysis of data from two European remote-sensing satellites showing the amount of water locked up in the ice sheet had risen slightly between 1992 and 2002.

Then the ice sheet began to confound computer-generated predictions.

By 2005, Greenland was beginning to lose more ice volume than anyone expected — an annual loss of up to 52 cubic miles a year — according to more recent satellite gravity measurements released by JPL.

The amount of freshwater ice dumped into the Atlantic Ocean has almost tripled in a decade.

Since Steffen started monitoring the weather at Swiss Camp in 1991, the average winter temperature has risen almost 10 degrees. Last year, the annual melt zone reached farther inland and up to higher elevations than ever before.

There was even a period of melting in December.

This is one of the things that people claimed was sooooo alarmist about the movie. It turns out Al Gore was actually understating the case.

Among the things that are less than 22 feet above sea level are: New York City, most of Florida, New Orleans, the San Francisco Bay area, massive parts of the Indian subcontinent, and most of China's cities. The consequences of a major melt in Greenland or a major melt in west Antarctica would be disastrous, and both ice sheets are showing signs of faster melting than was predicted.